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eshover
Senior Member

146 Posts

Posted - 02/04/2016 :  05:27:34 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
I have a 2008 BB All American with an air leak that is driving me crazy. It leaks all of the air out of both tanks overnight. I have checked every line and fitting with soapy water, all of the valves & fittings. Last night I left the parking brakes off to see if that made a difference and it didn't.
Can the compressor have an internal leak to cause this? Why do both tanks go down?
Thanks,
ED

RonF
Top Member

867 Posts

Posted - 02/04/2016 :  05:59:56 AM  Show Profile  Reply with Quote
If your check valve in the supply line coming from the compressor to the tank is not working, then yes that could be your problem. Follow your line off of the compressor and it will either be at the air dryer or the wet tank.

US Army retired CMBT
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eshover
Senior Member

146 Posts

Posted - 02/04/2016 :  11:01:05 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
Will try to locate when I get time. Thanks!
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g0ttadrift
Advanced Member

USA
258 Posts

Posted - 02/04/2016 :  5:15:04 PM  Show Profile  Reply with Quote
It could be from anywhere... does your bus have airbags? We've already had to replace them on some of our 2007 series. Also, we've had the ABS valves corrode and leak from the bodies. Good luck, there's also a check valve on the top of the wet tank on that series, it's almost impossible to see with the bus all the way up in the air. Those have leaked for us too. Keep us updated, I'm curious to know what it is.
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aaronwilmoth80911
Top Member

538 Posts

Posted - 02/05/2016 :  2:41:55 PM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
I second the air bags, assuming that your bus has them.
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slippert
Top Member

USA
630 Posts

Posted - 02/08/2016 :  08:04:52 AM  Show Profile  Click to see slippert's MSN Messenger address  Reply with Quote
Just a thought.... shouldn't air bags have a pressure protection valve on them... air in tanks should stop at 60psi... bags can go completly flat if they are leaking, but tank pressure should stop dropping at 60psi unless that pressure protection valve is bad..

Edited by - slippert on 02/08/2016 08:06:35 AM
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eshover
Senior Member

146 Posts

Posted - 02/08/2016 :  2:25:06 PM  Show Profile  Visit eshover's Homepage  Reply with Quote
This bus does not have air bags.
I am trying to find the check valve in the air tanks. I talked to the BB service dept here and they said the check valve is in the air tank. I don't know how it can be but I my have to pull the air tank down to get to the check valve if there is one on the top of the tank.
ED
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g0ttadrift
Advanced Member

USA
258 Posts

Posted - 02/08/2016 :  6:51:19 PM  Show Profile  Reply with Quote
I just double checked and the check valve should be the 90 degree elbow coming out of the rear of the left side tank. There is a pressure protection valve on top of the right side tank and those corrode and leak. You shouldn't have to drop the tank, as long as they're set up the same way. There's nothing consistent when it comes to the building of these buses.
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Thomasbus24
Administrator

USA
4544 Posts

Posted - 02/09/2016 :  04:49:27 AM  Show Profile  Reply with Quote
I second the motion to check the pressure protection valve. We've changed a lot of them for external leakage that will pull down both tanks. To verify check valve, charge system then dump wet tank...should see no drop on gauges. Next, dump primary tank...should see no drop in secondary gauge.

EXCEPTION: Some Internationals (maybe others) will show pressure drops down to 90 PSI before stopping, this is acceptable.

Blue Bird uses a PPV that looks something like this:
https://d2jocyn8o0ggnq.cloudfront.net/assets/products/velvac/product/032221/457095.jpg?1313803759

It has a rubber cap or flap thing on one end...spray with simple green and watch the bubbles blow!
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eshover
Senior Member

146 Posts

Posted - 02/09/2016 :  05:30:13 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
Thanks guys, great information!
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57fan
Senior Member

United States
148 Posts

Posted - 02/25/2016 :  8:41:10 PM  Show Profile  Reply with Quote
Some of the new Blue Bird buses have had issues with the one way check valve leading into the Pri and Sec tanks will get stuck due to all the carbon and crap caused by EGR engines. Most check valves will leak air if the loss is near 1 psi. If you drain a wet tank a a very small and i mean small rate you might see that all the tanks will leak down. this is normal for a check valve. a sudden loss is different. In addition we have seen blue bird sir pressure switches leak on newer buses (2014) under the dash panel... hope this helps.

Lead, Follow or get out of the way! Thomas Paine
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eshover
Senior Member

146 Posts

Posted - 02/26/2016 :  05:23:23 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
I drained the primary tank and the other tank stayed up. I have checked the blow off valve but I have not been able to locate any leaks yet.
This bus is a 2008 so not new enough for some of the ideas.

I do have a 2015 that was leaking down and found a blue plastic line on the top of the junction block near the radiator was leaking. The slip fitting was bad.
Ed
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Thomasbus24
Administrator

USA
4544 Posts

Posted - 02/26/2016 :  06:40:37 AM  Show Profile  Reply with Quote
I never even thought about the dash....Actia gauges have these crappy fittings that screw into the circuit board that runs the dash and an air line plugs into them. Crappy being the operative word here.
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